Containers which are used to encase pressurized components, such as for example battery cases, will require a pressure venting device formed in the container in order to vent any undesirable increase in internal pressure. By venting undesirable increases in internal pressure, the container is prevented from becoming a dangerous projectile, because of explosive forces resulting from the build up of excessive pressure within the container.
It has been proposed in U.S. Pat. No. 3,918,610 to Willis to place a pressure venting device in an aerosol can which encases pressurized contents. More particularly, Willis proposes that integral concavities be formed in the bottom of the container with integral hollow bridges interrupting the concavities and spanning opposing side walls thereof. A further key feature of this patent is the provision of a weakening line or score in the container wall transversely across the bridge.
A major drawback of the proposed Willis device is that during the manufacturing process the score is put into the container while it is flat, but as the concavities and bridges are formed the score becomes stretched by the forming, which results in an inconsistent score thickness. Thus, forming the bridges so as to have the scores extending transversely thereto, after scoring, causes the metal to thin out as it is being stretched around the form. Consequently, this thinning of the residual thickness of the scores causes erratic vent pressures.